Age remains the single greatest risk factor for Alzheimer's, greater even than having the gene found in many people with the disease, the study confirmed. But "what we have shown here is that physical activity diminishes the deleterious influence of age," said Ozioma Okonkwo, an assistant professor of medicine at the school who led the study.
People who exercised had less accumulation of "beta amyloid plaque," the proteins that build up in the brains of people who suffer from Alzheimer's Disease. They had less shrinkage of the hippocampus and less reduction in use of glucose in the brain, two other symptoms of the disease. And they had fewer neurofibrillary tangles, twisted fibers inside brain cells of people with Alzheimer's. When researchers tested the people who worked out, they did better on memory and visual-spatial tests.
An increasing amount of research has shown that exercise can help hold off Alzheimer's Disease, including this July study that the New York Times called "inspiring." The University Wisconsin research, published in November in the journal Neurology, adds strong evidence from examinations of the subjects' brains to support that conclusion.
"A large body of work, including observational and intervention studies, has shown that physical activity is beneficial for maintaining cognitive function and delaying the onset of [Alzheimer's Disease] and related diseases among older adults," the researchers wrote. "However, it is only recently that studies have begun to investigate the potential effects of physical activity on biological markers" associated with the disease.
People in the study were recruited from the Wisconsin Registry for Alzheimer's Prevention. About three quarters of them have a family history of the disease, which puts them at greater risk for developing it. They were assigned to the active group if they worked out at moderate intensity for 30 minutes a day, at least five times a week.
Okonkwo said his group's "observational study" needs to be followed up with a true controlled study in which people are assigned to work out for various amounts of time.
Nevertheless, he said, "exercise does have some real potency in diminishing one’s risk of Alzheimer's, assuming one was on that path to begin with."